In recent years, see-through displays have been attracting attention as the display devices for information display systems or digital signage. In a see-through display, the background (i.e., the rear-face side of the display panel) is visible in a see-through manner, thereby conducting displaying such that information which is displayed by the display panel is overlaid on the background. Thus, a see-through display has good appeal and eyecatchingness. Application of see-through displays to showcases and show windows has also been proposed.
In the case where a liquid crystal display device is used for a see-through display, its low efficiency of light utilization will be a detriment. The reasons for the low efficiency of light utilization of a liquid crystal display device are the color filters and polarizing plates, which are provided in generic liquid crystal display devices. The color filters and polarizing plates absorb light in specific wavelength regions or light of specific polarization directions.
This has led to the idea of using a liquid crystal display device of the field sequential method. Under the field sequential method, multicolor displaying is performed through time-division switching between colors of light with which a liquid crystal display panel is irradiated from an illumination element. This eliminates the need for color filters, thus improving the efficiency of light utilization. However, under the field sequential method, the liquid crystal display device is required to have a rapid response.
Patent Documents 1 and 2 disclose liquid crystal display devices having improved response characteristics because of an electrode structure being provided which is capable of switchably generating a vertical field or a lateral field across the liquid crystal layer. In the liquid crystal display devices disclosed in Patent Documents 1 and 2, a vertical field is generated across the liquid crystal layer in either one of the transition (rise) from a black displaying state to a white displaying state and the transition (fall) from a white displaying state to a black displaying state, while a lateral field (fringing field) is generated across the liquid crystal layer in the other. Therefore, the torque due to voltage application acts on the liquid crystal molecules in both of a rise and a fall, whereby good response characteristics are attained.
Patent Document 3 also proposes a liquid crystal display device which realizes rapid response by allowing aid alignment regulating force by an electric field to act on the liquid crystal molecules at both of a rise and a fall.
However, it has been found through a study by the Applicant that, when the liquid crystal display devices disclosed in Patent Documents 1, 2 and 3 are used for see-through display, the problem of background blur (it being perceived as double images) may occur, thus resulting in a deteriorated display quality.
Accordingly, the Applicant has proposed in Patent Document 4 a crystal display device which can prevent such problems. Each pixel of the liquid crystal display device disclosed in Patent Document 4 is able to switchably present a black displaying state of performing black displaying with a vertical field generated across the liquid crystal layer and a white displaying state of performing white displaying with a lateral field generated across the liquid crystal layer. Also, each pixel is able to present a transparent displaying state in which a rear face side of the liquid crystal display panel is visible in a see-through manner with no voltage being applied to the liquid crystal layer, thus preventing the problem of background blur (it being perceived as double images).